The pink form is uncommon, but if you come across a patch of bluebells that covers an acre or more, like the one along the Trillium Trail in Fox Chapel where these flowers were blooming in early May, some of them are likely to nonstandard colors—pink, pale blue, lavender, or white.
Gray describes the genus and the species (though he seems not to have run across any pink flowers):
MERTENSIA Roth. LUNGWORT
Corolla longer than the deeply 5-cleft or 5-parted calyx, naked, or with 5 small glandular folds or appendages in the open throat. Anthers oblong or arrow-shaped. Style long and thread-form. Nutlets ovoid, fleshy when fresh, smooth or wrinkled, obliquely attached by a prominent internal angle; the scar small. Smooth or soft-hairy perennial herbs, with pale and entire leaves, and handsome purplish-blue (rarely white) flowers, in loose and short panicled or corymbed raceme-like clusters, only the lower one leafy-bracted; pedicels slender. (Named for Franz Karl Mertens, a German botanist.)
Corolla trumpet-shaped, with spreading nearly entire limb and naked throat; filaments slender, exserted; hypogynous disk 2-lobed.
M. virginica (L.) Link. (VIRGINIAN COWSLIP, BLUEBELLS.) Very smooth, pale, erect, 2-6 dm. high; leaves obovate, veiny, those at the root 1-1.5 dm. long, petioled; corolla trumpet-shaped, 2-2.5 cm. long, many times exceeding the calyx, light blue (pinkish in bud), rarely white; nutlets dull and roughish. Alluvial banks, N. Y. and Ont. to Neb., and southw. Apr., May.
Flora Pittsburghensis makes an important original contribution to the botanical literature. Brunnera macrophylla is recorded as naturalized in Ohio and New York, but not in Pennsylvania. We have found it, however, deep in the woods in Bird Park in Mount Lebanon, some distance from any cultivated planting.
Siberian Bugloss looks very much like a species of Forget-Me-Not (Myosotis spp.), but is easily distinguished by its large heart-shaped leaves (thus the specific name macrophylla, which means “large-leaved”). These plants grew in Bird Park in Mount Lebanon, where they were blooming at the beginning of May.
Gray does not describe this species, but the quick description above should make identification straightforward.
Easily recognized by its columns of vivid blue flowers; seen most often beside railroads or along roadsides. This is certainly one of our most decorative weeds. These plants were blooming in mid-June at the edge of a parking lot in New Stanton.
Once in a while a plant will appear with pink flowers, usually fading to blue after they have been open for a while; a picture of one such is here.
Gray describes the genus and the species:
ÈCHIUM [Tourn.] L. VIPER’S BUGLOSS. Corolla with a cylindraceous or funnel-form tube; lobes rounded, spreading. Stamens mostly exserted, unequal. Style thread-form. Nutlets roughened or wrinkled, fixed by a flat base. (A plant name used by Dioscorides from echis, a viper.)
E. VULGARE L. (BLUE-WEED, BLUE DEVIL.) Rough-bristly biennial; stem erect, 3-9 dm. high; stem-leaves linear-lanceolate, sessile; flowers showy, in short lateral clusters, disposed in a long and narrow thyrse or in an open panicle; buds pink; corolla brilliant blue (rarely pale or roseate). Roadsides and meadows, locally abundant. June-Sept. (Nat. from Eu.)
Mrs. Dana, in How to Know the Wild Flowers, has this to say about our subject:
When the blueweed first came to us from across the sea it secured a foothold in Virginia. Since then it has gradually worked its way northward, lining the Hudson’s shores, overrunning many of the dry fields in its vicinity, and making itself at home in parts of New England. We should be obliged to rank it among the “pestiferous” weeds were it not that, as a rule, it only seeks to monopolize land which is not good for very much else. The pinkish buds and bright blue blossoms, with their red protruding stamens, make a valuable addition, from the aesthetic point of view, to the bunch of midsummer field-flowers in which hitherto the various shades of red and yellow have predominated.
In Wild Flowers Worth Knowing, Neltje Blanchan adds some of the traditional lore of the plant:
Years ago, when simple folk believed God had marked plants with some sign to indicate the special use for which each was intended, they regarded the spotted stem of the bugloss, and its seeds shaped like a serpent’s head, as certain indications that the herb would cure snake bites. Indeed, the genus takes its name from Echis, the Greek viper.